A gas turbine engine generally includes a fan and a core arranged in mechanical communication with one another. Additionally, the core of the gas turbine engine general includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air flows through an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gasses through the combustion section drives the combustion section and is then routed through the exhaust section, e.g., to atmosphere. In particular configurations, the turbine section is mechanically coupled to the compressor section by one or more shafts extending along an axial direction of the gas turbine engine.
The fan includes a plurality of blades having a radius larger than the core of the gas turbine engine; the fan and plurality of blades being driven by or rotatable with the one or more shafts. For certain gas turbine engines, the fan is a variable pitch fan such that the plurality of blades are each rotatable about a respective pitch axis by a pitch change mechanism. The pitch change mechanism may rotate each of the plurality of blades about their respective pitch axes by changing its angular position relative to the plurality of blades and the one or more shafts.
It can be beneficial, in certain embodiments, to include a feedback sensor, to measure a position of the pitch change mechanism relative to the plurality of blades to measure the pitch of the plurality of blades. Typically, the pitch change mechanism is positioned at least partially within or adjacent to the one or more shafts. Accordingly, in order to measure a position of the pitch change mechanism relative to the plurality of blades and the one or more shafts, the one or more shafts must include elongated slots or openings to provide a sensor with a line of sight to the pitch change mechanism. However, such a configuration may weaken the one or more shafts or require additional bolstering of the one or more shafts to accommodate the elongated slots or openings. Alternatively, a sensor may be placed within the one or more shafts, the sensor connected to a controller of the gas turbine engine using, e.g., a wireless communication network. However, such a configuration can be unreliable.
Accordingly, a sensor capable of measuring a position of the pitch change mechanism relative to the one or more shafts without requiring an elongated slot or opening would be useful. More specifically, a sensor capable of measuring a position of the pitch change mechanism relative to the one or more shafts through the one or more shafts would be particularly useful.